1. Field of the Invention
The present invention relates to a key mechanism, and in particular, to a key mechanism fitted in a computer input device. The key has an adjustable suspended axle positioned on the input device in a manner so that it can be pivoted and moved linearly.
2. Description of the Prior Art
Nowadays, the computer mouse has become almost a standard peripheral device that is equipped with every computer system. Besides functioning to move the cursor on the screen, the computer mouse also performs a very important and extremely useful function in ticking icons on the screen. Therefore, it is desirable to upgrade the key mechanism of a computer mouse to provide (1) a better feel of touch, (2) a stable depressing motion, and (3) a key mechanism that occupies less space within the housing of the mouse.
FIG. 1 illustrates a prior art key mechanism structure for a computer mouse 9. The computer mouse 9 has an upper housing 91 and a lower housing 92 that together house several conventional micro switches and other conventional mouse components 94, such as a PC board, a ball, etc. The computer mouse 9 has several keys 95, with each key 95 having a protrusion 951 extending down through the upper housing 91 and contacting a micro switch 96. A fixed-arm mechanism is used to provide a positioning and depressing function for the keys 95. According to this fixed-arm mechanism, each key 95 has an extending arm 952 having a located opening 953. The extending arm 952 extends into the interior of the computer mouse 9 and is coupled to a positioning pillar 911 of the upper housing 91. The extending arm 952 is also supported by a hook 912 extending down from the upper housing 91. Thus, the hook 912 acts as a fulcrum while the key 95 is depressed so as to function like a fixed-arm structure. When a key 95 is depressed by a user, the key 95 will downwardly curve the extending arm 952 to activate the micro switch 96, which not only provides a rebounding force, but also relocates the key 95 and its deformed extending arm 952.
In order to provide better feel of the touch on each key 95, and to upgrade the stability of the depressing motion on the key 95 (i.e., to achieve the accurate rebounding of the micro switch 96 when the key 95 is depressed), the extending arm 952 should be as long as possible such that the user will not feel the differences of the rebounding of the key 95 when the user applies force on any part of the key 95. However, the recent trend has seen the sizes of various computer input devices (including for computer mice) become smaller. In addition, add-on equipments and peripherals have become more and more popular, such as data gathering devices and storing devices, finger print identification devices, smart card reading devices, and memory card/memory stick reading devices. Therefore, given the size restrictions of computer input devices, it will be difficult to fit these devices inside the computer input device. To overcome this disadvantage, one possible solution is to keep the extending arm 952 short, but the user will need to endure a less-than-optimum feel when touching (i.e., depressing) the key 95, and the user may need to exert a greater force if the depressed portion of the key 95 is close to the hook 912. A second possible solution is to thin the thickness of the extending arm 952 near the hook 912, but this may lead to deformation of the extending arm 952 during molding or after extended use by the user.